The present invention relates generally to electrical cable connectors and relates particularly, but not exclusively, to separable connector modules for connecting together the operating components of an underground power distribution system by means of shielded electrical cable.
Separable connector assemblies for underground power distribution cable, or shielded cable, are watertight when assembled and may be readily separated into two or more units to break a cable connection. As such units are available separately commercially for various reasons and are individually subject to special design considerations, the are commonly referred to as "modules". Thus, a connection includes two or more matching modules assembled together.
One type of separable connector commonly used is known as a "rod and bore" type. A bore connector module having a receiving bore in a shielded, insulating housing and a grasping contact member in the bore receives a matching rod connector module having rod contact which is inserted in the bore and grasped by the bore contact member.
It is desirable to be able to operate such connectors while their cables are electrically active to interrupt the power. As the cables are generally carrying power at a voltage on the order of thousands of volts, separation of the contacts of the connector on a live cable results in the formation of an electric arc between the contacts. The arc will, unless promptly extinguished, eventually strike a ground plane such as the grounded shielding of the modules, and create a direct line-to-ground fault.
In present connectors, the bore is lined with ablative material and the rod is provided with an ablative arc follower of ablative material, a material which generates arc-extinguishing gases when subjected to an electric arc. The arc follower of the rod is a rod-shaped extension at the end of the metal contact rod and is generally somewhat smaller in diameter than the rod. When the contact rod is pulled from the contact member of the bore module, the resulting arcing passes between the follower and the bore lining. The exposure of the ablative material to arcing causes it to generate arc-extinguishing gases which rapidly extinguish the arc. This permits the connector to be utilized as a switch by being operated under live conditions, without creating a line-to-ground fault.
One problem with the present design of contact rod assemblies has been premature arcing between the contact rod and the receiving contacts when the modules are connected under relatively high voltage conditions, such as at about 20 kilovolts operating voltage. The premature arcing can result in extensive damage to the connector.